Reading 1

Unit 2- Reading 1

Page 18

What Time Is It?

Early humans did not need clocks. They did not need to know the time of day. They woke up when the sun appeared. They hunted or fished or farmed while the sun was shining.

They ate when they were hungry and went to bed when darkness came. Measuring time became important when people liyed in towns and cities. People needed clocks so they could work together.

THE EARLIEST CLOCKS

About 4,000 years ago, ancient Egyptians developed a 12-hour time system. They divided the day into 12 hours. The earliest clocks used sun shadows to show the hours of the day. A long piece of wood was marked into hours. A short piece of wood was put at one end of the long piece of wood. As the sun shifted across the sky, the short piece of wood created shadows on the long piece. These shadows showed the hours. This method of showing time was useful, but not very accurate. Later, round Sundials were developed.

They used sun shadows, too, but they were more accurate than the wood clocks. Sundials could measure time on sunny days. However, they did not work at night or when the sun was hidden by clouds. Also, people were confused to see the time on sundials vary with the seasons.

Over many years, different kinds of clocks were created to measure time during the day and at night. Candle clocks were used in ancient China, Japan, and Iraq.

A candle holder was divided by marks into hours. As the candle burned, the marks showed how many hours had passed. Greeks used water clocks made of two glass bowls. The bowls were connected by a small hole. The top bowl was filled with water. The water slowly ran into the bottom bowl through the hole.

The bottom bowl was marked into hours that measured time. Hourglasses worked in a similar way. The difference was that sand shifted from the top bowl into the bottom bowl. Water clocks and hourglasses functioned very well to measure time.

THE DEVELOPMENT OF MODERN CLOCKS

Soon clocks developed into wonderful art objects. Clocks were put into beautiful wooden boxes. The boxes were painted with flowers and birds. About 1,000 years ago, an Arab engineer added mechanical features to water clocks. He used the falling water to turn gears that opened doors and rang bells. These mechanical features gave later engineers the idea to develop mechanical clocks.

Mechanical clocks first appeared in China about 800 years ago. The idea spread to other places. A mechanical clock had to be wound with a tool every day. It had a complex system of springs and gears inside. The gears turned a dial on the front of the clock. The earliest mechanical clocks had one dial that showed only the hour. Later another dial was added to show minutes.

Most modern clocks are powered by batteries or electricity. They show hours, minutes, and seconds. Knowing the exact time is important in our complex world.